Twenty-five miles due south of Salt Lake City, a massive construction project is nearing completion. The heavily secured site belongs to the National Security Agency.

“The spy center” — that’s what some of the locals like Jasmine Widmer, who works at Bluffdale’s sandwich shop, told our Fox News team as part of an eight month investigation into data collection and privacy rights that will be broadcast Sunday at 9 p.m. ET called “Fox News Reporting: Your Secrets Out.”

The NSA says the Utah Data Center is a facility for the intelligence community that will have a major focus on cyber security. The agency will neither confirm nor deny specifics. Some published reports suggest it could hold 5 zettabytes of data. (Just one zettabyte is the equivalent of about 62 billion stacked iPhones 5’s– that stretches past the moon.

One man we hoped would answer our questions, the current director of the NSA General Keith Alexander, declined Fox News’s requests to sit down for an interview, so we stopped by the offices of a Washington think tank, where Alexander was speaking at a cyber security event last year.